Operation; Selecting The Operating Mode; Switching On / Off; Adjusting The Level - IMG STAGELINE STA-225 Mode D'emploi

6 Operation

6.1 Selecting the operating mode

Select the desired operating mode STEREO /
BRIDGE with the switch MODE (9) .
Stereo mode –
STEREO
In stereo mode, both channels are operated
independently of each other .
Bridge mode –
BRIDGE
The bridge mode is designed to obtain a
higher power at a single speaker . For this pur-
pose, both amplifier channels are combined
to a mono amplifier: The input signal at the
left channel is sent to the right channel addi-
tionally in an inverted way . Thus, the voltage
at the output is doubled when the speaker
is connected for bridge mode, as described
in chapter 5 .2 . A signal at the right input is
ignored . The volume is adjusted with the left
control L-CH .

6.2 Switching on / off

To prevent loud switching noise, always
switch on the power amplifier in an ampli-
fier system after all other units and switch it
off as the first unit after operation . Prior to
switching on, turn the volume controls (1) to
the left stop "MIN" .
Switch on the amplifier with the switch
POWER (5) . After the welcome message, the
display (3) shortly shows the adjustments
of the operating mode, the limiter and the
input attenuation (fig . 4) and then changes
to the standard operating indication (fig . 3) .
After switching-on, the LEDs PROTECT (2)
light up for a short time . During this time,
the switch-on delay for the protection of the
speakers is active .

6.3 Adjusting the level

Set the output of the mixer or preamplifier
to its rated level (0 dB) or the highest undis-
torted output signal . Turn up the controls (1)
until the maximum desired volume is reached .
When the adjustment has been changed, the
attenuation ATTEN of the input signal by
the controls is shown on the display (3) both
numerically (i) and graphically (j) for a few
seconds . Then the display is changed to the
standard indication again (fig . 3) . The LEDs
SIGNAL, −20 dB and −10 dB (2) and a vertical
bar (e) on the display indicate the output level .
If the display shows
CLIP ON
is overloaded . If the LIMITER LEDs light up, the
limiter circuit is active and prevents an over-
load of the amplifier (
cases, turn back the corresponding control (1) .
CAUTION Never adjust the amplifier to a
very high volume . Permanent
high volumes may damage
your hearing! The human ear
will get accustomed to high
volumes which do not seem to be that high
any more after some time . Therefore, do not
further increase a high volume after getting
used to it .

6.4 Power indication

The standard indication during operation
(fig . 3) shows the output power of both
speaker outputs in the first line (a) . This value
has been calculated according to the out-
put voltage measured and a load impedance
assumed . The specified load impedance is
always 8 Ω after switching on the amplifier .
If 4 Ω speakers are connected, press the
button LOAD 4 / 8 OHM (4) to adapt the cal-
culation . The display now shows
and the power is calculated for a load imped-
ance of 4 Ω . To switch back, press the button
repeatedly until
play switches back to standard indication a
few seconds after the last press of the button .
Note: The power indicated is not effective in bridge
mode .

6.5 Groundlift switch

If an interfering hum noise can be heard with-
out a music signal, a ground loop may be
the reason for this . Ground loops may occur
if two units have contact both via the signal
ground and via the earthed conductor of the
power supply or a conductive connection of
the housings in the rack . To separate such a
ground loop, set the switch GROUNDLIFT (8)
to the position LIFT .

7 Protective Circuits

The protective circuits are provided to prevent
damage to the speakers and the amplifier .
The integrated level limiter reduces the input
signal when the limit level is reached at the
output . If the amplifier is overloaded, distor-
tions can thus be prevented which could dam-
age the speakers . With the switch LIMITER
(10), this function can be switched on and
off [indication
, the input Due to an additional protective circuit,
the speakers are separated from the output
All rights reserved by MONACOR
may be reproduced in any form or by any means for any commercial use.
☞ chapter 7) . In both
(k)
OUT 4Ω
OUT 8Ω is shown . The dis-
or (g)] .
LIMT ON LIMT OFF
INTERNATIONAL GmbH & Co. KG. No part of this instruction manual
®
of the channel concerned . If it is active, the
correspond ing red PROTECT LED (2) lights up:
1 . for a short time after switching-on
(switch-on delay)
2 . in case of overload / overheating, the indi-
cation (c) additionally changes
PROT OFF
to on the display (3)
PROT ON
After cooling-down, the amplifier channel
continues its operation .
In standard mode, the display shows the tem-
perature at the power transistors separately
for both channels (d) . With higher tempera-
tures, the fan control ensures that the fan of
the channel concerned runs at higher speed .
If a PROTECT LED does not extinguish
after switching-on or after cooling-down after
an overload, the amplifier must be switched
off and the cause for the defect must be
eliminated .

8 Specifications

RMS output power
stereo at 4 Ω 2 × 350 W
stereo at 8 Ω 2 × 250 W
bridge mode at 8 Ω
Input sensitivity for
rated power at 8 Ω 1.3 V
Input impedance 10 kΩ
Frequency range 10 Hz – 50 kHz
THD < 0.1 %
Channel separation > 50 dB
S / N ratio > 80 dB
Connections
Inputs XLR and 6.3 mm
jacks, balanced
Outputs screw terminals and
speaker jacks
(Speakon compatible)
Ambient temperature 0 – 40 °C
Power supply 230 V/ 50 Hz
Max. power consumption 1500 VA
Dimensions (W × H × D) 482 × 100 × 330 mm
Rack spaces 2 RS
Weight 10.3 kg
Subject to technical modification .
700 W
9